Re: "a bunch of bull"

: : : : Yes. "Bull" is short for "bullshit," which means nonsense, bragging, empty talk, exaggeration, lies--that sort of thing. The Dictionary of American Slang says it originated in student use about 1915 and became widespread after use in the U.S. Navy during World War I.

: : : In my time during my National Service in the RAF in the 1950s, and I suspect still current in the British military, 'bull' was used to describe the meticulous cleaning of personal and communal property that new recuits were forced to adopt, An example would be the Drill Sergeant saying 'get those boots bulled up, airman.'
: : : The word was less commonly used in the given context, above.

: : I rather suspect that "bull" meaning empty or boastful talk was in use long before the American "bullshit". Did "..a bunch of bull.." proceed from bull or bullshit?

: The Dictionary of Amer. Slang says "bull" in that sense probably came from "bullshit." About "a bunch of," I don't know--I'd guess it's just one of several elaborations that a speaker could use, including "a pile of . . . ."

M-W.com dates "bull" meaning nonsense to 1640 and dates "bullshit" meaning nonsense to 1915. Now if The Dictionary of Amer. Slang says "bull" meaning nonsense derives from "bullshit" then whom do we believe?